1. Field of the Invention
The present invention relates generally to firmwave associated with a hard disk drive and more particularly to a method and apparatus for reducing the acoustic noise generated by movements of data read/write componentry of a hard disk drive assembly, to reduce settling time and provide accurate head positioning.
2. Background Information
Hard disk drives include a plurality of magnetic transducers that can write and read information by magnetizing and sensing the magnetic field of a rotating disk(s), respectively. The information is typically formatted into a plurality of sectors that are located within an annular track. The are a number of tracks located across each surface of the disk. A number of vertically similar tracks are sometimes referred to as a cylinder. Each track may therefore be identified by a cylinder number.
Each transducer is typically integrated into a slider that is incorporated into a head gimbal assembly (HGA). Each HGA is attached to an actuator arm. The actuator arm has a voice coil located adjacent to a magnet assembly which together define a voice coil motor. The hard disk drive typically includes a driver circuit and a controller that provide current to excite the voice coil motor. The excited voice coil motor rotates the actuator arm and moves the transducers across the surfaces of the disk(s).
When writing or reading information the hard disk drive may perform a seek routine to move the transducers from one cylinder (track) to another cylinder. During the seek routine the voice coil motor is excited with a current to move the transducers to the new cylinder location on the disk surfaces. The controller also performs a servo routine to insure that the transducer moves to the correct cylinder location.
Many disk drives utilize a xe2x80x9cbang-bangxe2x80x9d control loop for the servo routine to insure that the transducer is moved to the correct location. The shape of the current waveform for seek routines that utilize bang-bang control theory is typically square. Unfortunately, square waveforms contain high frequency harmonics which stimulate mechanical resonance in the HGA causing acoustic noise.
It is always desirable to minimize the amount of time required to write and read information from the disk(s). Therefore, the seek routine performed by the drive should move the transducers to the new cylinder location in the shortest amount of time. Additionally, the settling time of the HGA should be minimized so that the transducer can quickly write or read information, once located adjacent to the new cylinder.
The mechanical resonance created by the square waveforms of the prior art tend to increase both the settling and overall time required to write or read information from the disk. It would therefore be desirable to provide a seek routine that minimizes the mechanical resonance of the HGA, thereby decreasing acoustic noise and reducing settling time.
One embodiment of the present invention is a hard disk drive which moves a transducer across a disk surface so that the transducer has an essentially sinusoidal acceleration trajectory. The essentially sinusoidal acceleration trajectory of the transducer may reduce the excitation of mechanical resonance of a head gimbal assembly embodying the transducer, to reduce acoustic noise in the HGA and other componentry of the hard disk drive. Reduction of acoustic noise reduces settling time and provides accurate positioning of the transducer relative to a desired track of the disk.